1. Field of the Invention
This invention relates to a process for the preparation of asymmetrical alkaline earth metal organoborates, organoaluminates, organoarsenates, and organophosphates.
2. Description of the Prior Art
Organoborates of the type M (BR.sub.3 R').sub.n are relatively simple species to prepare. The usual route is to react a symmetrical borane, BR.sub.3, with an organometallic reagent such as butyl lithium or dibutylmagnesium. The procedure to make compounds of the type M(BR.sub.2 R'.sub.2).sub.n is complicated by the fact that one of the starting materials must be an asymmetrical borane, BR.sub.2 R'. None of the methods known for accomplishing this result are commercially practical.
Klemann et al in U.S. Pat. No. 4,060,674 prepare alkali metal analogs of the asymmetrical alkaline earth metal organoborates and aluminates of the invention by reacting monoorganoalkali metal compounds with polyorganometallic compounds in an organic solvent.
Damico in J. Organic Chemistry, 29(7), 1971-1976 (1964) disclose the preparation of alkali metal analogs of the asymmetrical alkaline earth metal organoborates of the invention by reacting alkyl lithium and alkyl sodium with trialkyl boranes.
Malpass in U.S. Pat. No. 4,231,896 and U.S. Pat. No. 4,325,840 disclose the preparation of organomagnesium complexes of the formula: EQU (R'.sub.2 Mg).sub.m (RM).sub.n
wherein RM is an organoboron compound, R is a primary, secondary, or tertiary alkyl group, R' is a primary C.sub.1 -C.sub.10 alkyl or phenyl group, or mixture thereof, and m and n are numbers such that the ratio of m over n is about 1 or greater. These complexes are prepared by reacting magnesium metal with a primary alkyl halide or aryl halide in the presence of a hydrocarbon solvent and, directly thereafter, adding an organoboron compound selected from the group consisting of trialkylboron, dialkylboron halide or alkylboron dihalides. Alternatively, the organoboron compound can be generated in situ by alkylation of a boron salt by the organomagnesium prepared by the above reaction of magnesium metal with a primary alkyl halide or aryl halide. The resultant organoboron compound then serves as a solubilizing agent for excess alkyl or aryl magnesium compound. The asymmetrical alkaline earth metal organoborates of Malpass are useful as components of electrolytes in electrochemical cells.